#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

char *fcvt(double x, int n, int *dp, int *sign)
{
    char tmp[1500];
    int i, lz;

    if (n > 1400U) n = 1400;
    sprintf(tmp, "%.*f", n, x);
    i = (tmp[0] == '-');
    if (tmp[i] == '0') lz = strspn(tmp+i+2, "0");
    else lz = -(int)strcspn(tmp+i, ".");

    if (n<=lz) {
        *sign = i;
        *dp = 1;
        if (n>14U) n = 14;
        return "000000000000000"+14-n;
    }

    return ecvt(x, n-lz, dp, sign);
}
